Fracture fixation of long bones such as the femur, tibia, humerus, fibula, or other long bones is challenging because of the difficulty of properly aligning and then securing fractured bone segments in place to allow the bone to heal. One very effective means of securing such fractures is intramedullary nailing. Intramedullary nailing is well-known in the art and essentially entails aligning two or more segments of bone that result from a fracture about a rod or nail that fits down the medullary canal of the fractured bone. Various techniques for intramedullary nailing are discussed in U.S. Pats. Nos. 5,951,561 and 6,010,506, which are hereby incorporated by reference.
Whether fixation is by intramedullary nailing or by some other means, the repositioning of the segments of a long bone fracture (fracture reduction) is one of the most challenging aspects of fracture fixation. The contraction of soft tissue subsequent to a fracture tends to shorten the fractured limb and place the fractured segments of the bone out of alignment relative to each other. Repositioning these segments to restore anatomic alignment can be very challenging.
One technique for realigning fractured bones comprises the use of a fracture table to first distract a limb back to its original length. When a patient is positioned and secured on the fracture table, a surgeon may then manipulate segments laterally to realign the segments. However, fracture tables are expensive and many surgeons do not use them due to cost, availability, or the limitations of having a patient fixed in one position. Multiple intra-operative x-ray or fluoroscopic images may need to be taken to assure alignment of the segments in all planes. Additionally, a fracture may continue to shift out of alignment as fixation is applied.
Another method for fracture reduction includes the attachment of an external distraction device to the bone via bone pins that pass through soft tissue and attach to the bone. These types of devices allow a surgeon to turn a threaded knob or other actuator and pull a fracture apart. Once distracted, repositioning is then accomplished by manual, physical manipulation of the limb. Once again, multiple intra-operative x-ray or fluoroscopic images may be necessary to assure proper realignment of the segments, and segments may shift out of alignment as fixation is applied.
Another method for fracture repositioning or reduction is through the use of the Internal Fracture Reduction Device manufactured by Smith & Nephew, Inc. This device is inserted into a portion of the fractured long bone and allows manipulation of a segment of the fractured bone. However, such a device must be inserted over a guide rod that has already been placed through the medullary canal of all fractured bone segments. Therefore, placement of the guide rod first requires at least adequate fracture alignment to place the guide rod through the realigned medullary canal.
Smith & Nephew, Inc. also manufactures a reducer for use with its TRIGEN® brand intramedullary nailing system. As shown in FIG. 1, the reducer 100 is an elongated, cannulated tube 101 with a connector 102 for attaching a handle 103. The inner diameter of the tube 101 is large enough to accommodate the passage of a guide rod (not shown). The outer diameter of the tube 101 is small enough to be inserted into a long bone without reaming the bone. The tube 101 is typically formed to the same shape as the intramedullary nail that will subsequently be implanted in the bone. The distal tip of the tube 101 includes a finger 104 that is bent up slightly. This finger 104 serves several purposes.
First, the finger 104 can be used to deflect a guide rod as the end of the guide rod passes the end of the tube 101. Specifically, the guide rod may be deflected in a desired direction by rotating the reducer 100 such that the distal end of the finger 104 is pointed in the desired direction. Second, the finger 104 places resistance on a guide rod that passes into or through the finger 104, thereby holding the guide rod in position relative to the reducer 100 by friction. Third, the curved tip of the finger 104 allows the reducer 100 to be pushed smoothly through the medullary canal of a proximal segment and into a distal segment. While the TRIGEN® system reducer has significant advantages, multiple intra-operative x-ray, fluoroscopic, or other such images must still be used to assure proper alignment of the segments in all planes as the reducer 100 is inserted.
Several manufactures currently produce image-guided surgical navigation systems that are used to assist in performing surgical procedures. The TREON™ and iON™ systems with FLUORONAV™ software manufactured by Medtronic Surgical Navigation Technologies, Inc. are examples of such systems. Systems and methods for accomplishing image-guided surgery are also disclosed in U.S. S No. 60/271,818 filed Feb. 27, 2001, entitled Image Guided System for Arthroplasty, which is incorporated herein by reference as are all documents incorporated by reference therein. Further image-guided surgery devices, systems, and methods are disclosed in a provisional application entitled SURGICAL NAVIGATION SYSTEMS AND PROCESSES, Application Serial No. 60/355,899, filed on Feb. 11, 2002, hereby incorporated by this reference.
The Medtronic systems use fluoroscopic imaging to capture anatomical characteristics and infrared cameras that detect certain targets placed in the surgical field to track instruments and anatomy. As used herein, an infrared camera can be any type of sensor or detector that is capable of sensing or detecting light of an infrared wavelength. Any number and orientation of so-called targets, fiducials, frames, markers, indicia, or any other desired location-assisting functionality (“references”) can be used as targets to be detected by an imaging system or sensor. Other imaging or data capture systems such as CT, MRI, visual, sonic, digitized modeling, traditional x-ray equipment, or any other effective system or technique which has the capacity to image bone or other desired structures or tissue in the body can be used. Such systems generally include transducer functionality for emitting energy or otherwise performing sensing or location of objects and anatomical structure, a processor, mass memory storage, input/output functionality to control and direct operation of the system, and at least one monitor or other visual output functionality for rendering images that may be constructed by the system, whether or not in combination with images obtained from the transducer in real time.
Such systems typically combine processes and functionality for obtaining, storing, manipulating and rendering images of internal body structure with functionality that senses, stores, manipulates and virtually renders representations of components or objects such as instrumentation, trial components, surgical tools and other objects. The systems can then generate and display representations of the objects in combination with images of the body structure or tissue. Such combination renderings can be created using real time imaging of the body structure or tissue, or the system can obtain appropriate imaging of such structure or tissue and later computer generate and display renderings of it. The Medtronic systems, for instance, require the use of references attached to the anatomy, typically in a rigid fashion, such as to bone structure. The system tracks movement of the reference in three dimensions and then generates images of the bone structure's corresponding motion and location.
The references on the anatomy and the instruments either emit or reflect infrared light that is then detected by an infrared camera. The references may be sensed actively or passively by infrared, visual, sound, magnetic, electromagnetic, x-ray, or any other desired technique. An active reference emits energy, and a passive reference merely reflects energy. In some embodiments, the references have at least three, but usually four, markers that are tracked by an infrared sensor to determine the orientation of the reference and thus the geometry of the instrument, implant component or other object to which the reference is attached. References have been attached to surgical and implant devices such as instrumentation, trial instruments, and the like. For example, references have been attached to probes, instruments for placing acetabular cups and trial implants, drill guides, and cutting blocks.
The Medtronic imaging systems allow references to be detected at the same time the fluoroscopy imaging is occurring. Therefore, the position and orientation of the references may be coordinated with the fluoroscope imaging. Then, after processing position and orientation data, the references may be used to track the position and orientation of anatomical features that were recorded fluoroscopically. Computer-generated images of instrumentation, components, or other structures that are fitted with references may be superimposed on the fluoroscopic images. The instrumentation, trial, implant or other structure or geometry can be displayed as 3-D models, outline models, or bone-implant interface surfaces.
Current systems and techniques do not provide for effective image-guided reduction of fractures. Improved products and methods would include structures and techniques for guiding a reducer through the medullary canals of two or more bone segments that have been created by a fracture of a bone. Improved products and methods would also provide for reduced numbers of x-ray, fluoroscopic, or other images, and would not necessitate pre-operative imaging or surgical procedures prior to the primary procedure. Further, improved products and methods would allow alignment of bone segments to occur using images of at least one of the bone segments in combination with images of one or more implements, instruments, trials, guide wires, nails, reducers and other surgically related items, which are properly positioned and oriented in the images relative to the bone segments. Further, improved products and methods would provide for updated monitoring of bone segment positions, and therefore, rapid alignment of bone segments.